This invention relates to an electrophotographic apparatus, such as a laser beam printer and a copying machine, whose toner hoppers and developers can be replaced by its user or a maintenance engineer.
Referring to FIG. 7, the general configuration of a laser printer whose toner hopper 1 and a developer 2 can be replaced by its user will be explained. For example, an electrophotographic apparatus is typically equipped with one or more printing sections comprising a photoreceptor 8, a charger 9 that electrically charges the surface of the photoreceptor 8, an optical scanning section 10 that optically scans the surface of the charged photoreceptor 8 with a laser beam, a developer 2 that develops image areas that are scanned optically, a toner hopper 1 that supplies toner 11 to said developer 2, and an image transfer unit 13 that transfers the developed image to a recording member 12. With such an arrangement, it is possible to print multi-color images on a single laser printer by replacing the set of elements consisting of the toner hopper 1 and the developer 2. This is also applicable to MICR toner (toner for magnetic ink character recognition).
In the above-described laser printer, a user or a maintenance engineer replaces the toner hopper 1 and the developer 2. At the time of this replacement, the toner hopper 1 (for example, containing red toner) may be combined with the wrong developer 2 (for example, containing a blue toner), so that the image printing may fail. To prevent this, various contrivances have been proposed.
Referring to FIG. 8, one of the conventional techniques used in full-color laser printers will be explained. This example is comprised of a slit disk 16 that is mounted on the shaft of a rotating means 15 disposed in a toner cartridge 14, which disk 16 has some equally-spaced slits on its circumference; a photo sensor that is provided opposite to the slit disk 16 to detect the presence of respective slits of the disk 16 as the disk rotates; a pulse signal generator 18 that generates a pulse signal responsive to detection of each slit of the disk 16 as the disk rotates; and a detector 3 that detects the kind of a toner cartridge 14 from the pulse signal. Generally, a full-color laser printer contains four printing sections which provide for use of four kinds of toner (yellow, magenta, cyan, and black) to form color images. Therefore, the laser printer requires four toner cartridges 14. Similarly, the pulse signal generator 18 must have four slit disks 16 that have different slit intervals to distinguish the toner cartridges 14 properly. (For example, see Japanese Application Patent Laid-Open Publication No. 2001-255728 (Page 3–7, FIG. 3))
Referring to FIG. 9, a general technique for effecting proper combination of a toner hopper and a developer will be explained. FIG. 9A shows a means to prevent a wrong combination of toner hoppers and developers. FIG. 9B shows examples of a key configuration used for this purpose. In FIG. 9A, plural keys 19 are provided in the part where the toner hopper 1 is connected to the developer 2 to prevent wrong hopper-developer combinations. FIG. 9B-(i a) shows the shape of a key 20 for a toner hopper containing red toner and the shape of a key 21 of the developer 2 containing red toner. The projection and recess of these keys are formed to fit each other. Similarly, FIG. 9B-(b) shows the shape of a key 22 for a toner hopper containing blue toner and the shape of a key 23 of the developer 2 containing blue toner. The projection and recess of these keys are formed to fit each other. However, in FIG. 9B-(c), it can be seen that the key 22 of the toner hopper containing blue toner does not fit to the key 21 of the developer 2 containing red toner.
Generally, a full-color laser printer uses four kinds of toner (yellow, magenta, cyan, and black) to form full color images. In other words, the printer requires four toner hoppers and four developers. Therefore, a spot color printer that has at least one printing section and forms images without mixing toners must prepare some dozens of toner colors to meet a user's requests.